The research on RF output envelope of C-band Multi-Beam Klystron

The shoulder and the tilt of RF output envelope of the C-band broadband MBK are described and discussed in the paper. The RF envelope shoulder occurs mainly at low part of the operating frequency band, and is caused by the gassing of microwave attenuation material FeSiAl covering on the wall of the cavity. The RF envelope tilt is caused by the drop of the pulse voltage and the dependence of efficiency on the beam voltage. These physical phenomena are explained and analyzed in the paper. The methods for overcoming the RF envelope shoulder and reduce the RF envelope tilt are also discussed.